Power semiconductor devices, such as those fabricated from SiC (silicon carbide), may be designed to operate at very high operating temperatures (e.g., greater than 250° C.). Such power semiconductor devices may be bonded to a cooling device, such as a heat sink or a liquid cooling assembly, for example. The cooling device removes heat from the power semiconductor device to ensure that it operates at a temperature that is below its maximum operating temperature. The bonding layer that bonds the power semiconductor device to the cooling device must be able to withstand the high operating temperatures of the power semiconductor device.
Transient liquid phase (TLP) sintering (TLPS) or diffusion bonding or soldering are methods of high temperature bonding that may be used to bond one substrate to another (e.g., a power semiconductor to a cooling device). For example, TLP bonding results in a bond layer having a high temperature melting point. A typical TLP bond consists of two different material compounds: a metallic layer and an intermetallic layer or alloy. Generally, the intermetallic layer having a high-remelting temperature is formed during an initial melting phase wherein a low melting temperature material, such as tin, diffuses into high melting temperature materials, such as copper, silver, or nickel. Conventional methods for heating TLP sintered interconnect microstructures have utilized convection ovens with considerable thermal masses and gradual heating profiles. Such considerable thermal masses and gradual heating profiles may result in an increased formation of voids in a bonding layer, resulting in a weaker bonding layer.
Accordingly, a need exists for alternative methods for heating TLP sintered interconnect microstructures to form a more strengthened bonding layer with less voiding between a pair of substrates.